Add generated CITATION.cff

[kernelpanic888]

Related to #784.

This adds a generated CITATION.cff while keeping package.json as the source of truth.

What changed:

• added a small bin/citation-cff.js generator with no new dependencies;
• added npm run citation;
• added repository metadata to package.json;
• committed the generated root CITATION.cff so GitHub can show "Cite this repository" immediately.

The generated CFF uses the current package.json name/description, author, contributors, license, version, and repository URL.

Local checks:

• npm run citation;
• node --check bin/citation-cff.js;
• generated output matches the committed CITATION.cff;
• parsed CITATION.cff as YAML;
• git diff --check.

I did not run the full project lint because dependencies are not installed in my local checkout. I also could not run cffconvert --validate because cffconvert is not installed in this environment.

[nichtich]

Thanks for contribution. I wait to merge because we first need to discuss proper CITATION.cff in our team. I'd like to roll out for all of our repositories in a consistent way and not having to add a conversion script to every repository.

[kernelpanic888]

Thanks, that makes sense. I'll wait for the team decision and am happy to adapt this PR to whatever repository-wide approach you settle on.